Carbon structural steel is a kind of carbon steel. Carbon content is about 0.05%- 0.70%, which can be as high as 0.90%. It can be divided into ordinary carbon structural steel and high quality carbon structural steel.Ordinary carbon structural steel contains more impurities so its price is low. It is usually used in industry with low performance requirements. It has a carbon content of less than 0.30% and the content of manganese content less than 0.80%. The strength of ordinary carbon structural steel is low, but the performance of plasticity, toughness and cold deformation is excellent. In addition to a few cases, it can be used directly without heat treatment. It can be made into strip steel, special-shaped steel, steel plate, etc. It is mainly used for railway, bridge and various construction projects, and makes all kinds of metal components that bear static load and non-important mechanical parts and ordinary welds which do not need heat treatment.The steel of high quality carbon structural steel is pure, with few impurities and good mechanical properties. It can be used after heat treatment.